1. Field of the Invention
The invention relates generally to the field of photography and particularly to camera apparatus wherein the photographer is alerted if the battery source voltage is too low to adequately power a particular camera operation, such as autofocusing.
2. Description of the Prior Art
An automatic focusing camera having a built-in electronic flash is disclosed in U.S. Pat. No. 4,214,827, issued July 29, 1980, wherein the shutter blades cannot be released if either the power source voltage for activation of the automatic focus adjusting means or the power source voltage for activation of the flash means is lower than a corresponding predetermined voltage level. The predetermined voltage level is one which is sufficient for the automatic focus adjusting means and/or the flash means to enable a correctly focused exposure under various light conditions. When a shutter release button on the camera body is manually depressed to initiate picture-taking, but the shutter blades are not released because the power source voltage is below the predetermined voltage level, the photographer is thereby alerted to change the batteries. A problem, however, is that the photographer may not realize that the shutter blades have not been released. Consequently, an erroneous decision to take a picture may be made.
Another autofocusing camera having a built-in electronic flash includes a light emitting diode (LED) on the camera body which is illuminated whenever the flash capacitor is being charged by battery-powered flash charging or voltage boosting means. The LED is turned "off" only after the flash capacitor is sufficiently charged to fire the flash tube to provide the required flash illumination. Since a relatively long time, e.g. 30 seconds, to charge the flash capacitor indicates weak batteries, the photographer knows to change the batteries if the LED remains illuminated for that time. The problem, however, is that the electrical performance of most batteries is substantially different for flash charging and autofocusing operations, and therefore a long time to charge the flash capacitor may not be an accurate enough measure to determine that the power source voltage is too low for proper autofocusing. Consequently, a picture may not be correctly focused.